Elevator control system



Dec. 5, 1933.

E. M. BOUTON 1,937,808

ELEVATOR CONTROL SYSTEM Filed June 24, 1924 '7 Sheets-Sheet 1 lf/f?Lil/2f? 6 N1 6F www M /MF M F F1 @F1 @91' oor Sw/ces A/ [H215L 4/1 dEmer enc fw/'c/z D Y f 6F\ 7L/'m/f- Jw//hes UV] 467-\ F[Il] [l ff/Q0mg/QM ATTORNEY Dec. 5, 1933. E. M. BOUTON ELEVATOR CONTROL SYSTEM FiledJune 24, 1924 7 Sheets-Sheet 2 15b QE,

down-1TB 62 LlIJ/ 6 INVENTOR foyar/Or/fof? WITNESSESZ DCC. 5, 1933. E.M. BOUTON ELEVATOR CONTROL SYSTEM Filed June 24, 1924 '7 Sheets-Sheet 360 0o0n5`w/c`h 7.9

Door Sn//YC/les 2nd Hoor Wwf Ey. 2'

7U /0 WITNl-:ssEs: l `UG INVENTOR M 6j 207D- Edgar M. 5cl/fon ATTO R NEY Dec. 5, 1933. E. M. BOUTON 1,937,808

ELEVATOR CONTROL SYSTEM Filed June 24, 1924 7 Sheets-Sheet 4 Dec. 5,1933. E, M BQUTQN 1,937,808

ELEVATOR CONTROL SYSTEM Filed June 24, 1924 7 Sheets-Sheet 5 A INVENTOREdgar/75a afa/1 BY t ORNEEY Dee. 5, 1933.

E. M. BoUToN 1,937,808

ELEVATOR CONTROL SYSTEM Filed June 24. 1924 '7 Sheets-Sheet 6 Dec. 5,1933. E. M. BOUTON ELEVATOR CONTROL SYSTEM 1924 7 Sheets-Sheet 7 FiledJune 24 INVENTOR Edgar loazol? A RNEY vim l 55 familiar manner.

v1 y Patented Dec. 5, 1933 YELEVATOR CONTROL SYSTEM Edgar M. Bouton,East Pittsburgh, Pa., assignor to Westinghouse Electric & ManufacturingCompany, a corporation of Pennsylvania Application June 24,1924. serialNo. 122,647

16L Claims. (ci. 1in- 29) n My invention relates to systems of controland it has particular relation' to systems employed in connection withelevators, hoists and similar machines.

ifi One object of my inventionis to provide a system ofA control whereby`an elevator cai' is maintained in a definite schedule of stops that maybe predetermined.

A second object of my invention is to provide a system of controlwhereby the operation of the elevator is effected by means ofpush-button switches and wher'eby'a plurality oi cars may besimultaneously controlled to maintain 'an eili- V k, cient scheduler ofoperation. 15n Other objects of my invention willy be apparent from thefollowing description andthe claims appended thereto.-

My invention will be described in connectionl with the accompanyingdrawings in which,

Figure l is a diagrammatic view of the main circuits of acontroll systemembodyingmy invention; V

Figs. 2 and.3 are diagrammatic views' ofthe .control circuits employedirl-'connection with 25y Fig. 1; y p

Fig. 4 illustra-tesV a terminal board for modifying" the connectionsillustrated in Fig. 3;

Fig. 5 is a diagrammatic view illustrating another form of my invention;Fig. 6 illustrates certain connection'semployed for-push-buttonoperation in connectioirwithv the systems illustrated in Figs. 2 andl 3,and

Fig.r 7 illustrates a `door switch employed inr inFigs. 5, 6 and 7 alsoshown in wiring diagram*Y form.-

My invention will bedescribed first in connection with Figs. 1, 2, 3*andV 4, wherein Athe elevator car is" operated on a denitejschedule and`makes certain stops only'. A dispatcher or other authorized person maypredetermine the 50' `stopiitlfiat the car is to -makeby reason'of theterminal board 'connections'illustratd in Fig. 4.rr

The" car operator cannot `change this schedule and he actsV only asaconductorto announce'the oors and to open and,l close therdoors .in a`loop circuit with the motor armature.

opening any door.

With reference to Figs; 1 and 9, an elevator motor, having an armature Mand separately excited field-magnet windings Fl and F1, is adapted to beenergized from a variable voltage generator having an armature G.connected'in 60 The generator isprovided with a separately excited`field winding GF for controlling the generator voltage and thedirectiony of operation of the elevatorl motor in ya familiar manner.The generator 65 armature is normally continuously driven byY anysuitable prime mover, such as the illustrated motor M1.

Referring to Figs. 2 and 9, direction switches l 1, 2, 3 and 4 controlthe generator i'ield winding 70' GF. Relay BR controls the brakemagnet'coil B which is of the usual shunt type, and relay FR controlsthe motor standing lield winding F. kThe direction switch coils 1', 2',`3 and 4" are energized through a pair-'of up and down relays UR and DR,and `relays IR and GFi and pro-` vided for eiecting speed control, GFibeing con- '.trolled in accordancewithtme counter E. M. F. of

the motor, tocontrol the degree. of the generator field excitation: v80`Up and down relays USi and DS1 connect vthe operating coil of relay IRto the separate source ofencrgy. p and down speedrelays` USzy and D82control the operating coil of relay 2R. Relay l2R is adapted to`connectthe operating coilyof relayfMF tothe elevator-motor armature.

Relay MF controls relay FRi which, in turn,

controlsthe motor extra el'd winding F1. .A pair of levelling switchesvUL and DL are con'-H trolled in a well-known manner whereby Atheyare-normally 1*retire`d or retracted, by ak suitablemag'net lcomprisingcoils UL and DL. The levelling switches are rendered eiectivej upon Theswitches are actuated by means of suitable cams 101 (Fig.-8) that aredisposed at points in the elevator hatch-way adjacent to the variousfloors, for the welleknownv purpose of Ymaintainingr the elevatorcar ata' proper level. fr f A fioor-stop-device, such as commonlyv'em- 100ployed in `connection with pushvbutton elevators, Ais provided, 'havingthree switches, "such` as 62, 64 and 65 at each intermediate floor foreach direction of travel andcontrolling a'plurality of oor relays 11 to15 inclusive (Figs. 3 and 10.). 105

VThe licor relays, inaccordance with my sys-VV tem, are controlled bymeans of an auxiliary device which I shall term ,a floor selector. Thisydevice may be x'nechan'icallyV4 connected to the elevator 'as' is theordinary geared-limit." 110 `switch and similarly comprisesprogressively acwhen the car is adjacent to the second iloor,l

but open again when leaving the floor. A pushbutton station 16 of thewalking-beam type (see Figs. 5 and 10) is located `in the elevator carfor determining the up and the down. direction of the motions of theelevator and this switch remains closed during the v4entire up and downmotions of the elevator. y. Y Y 5 The operation oi1 this form of mycontrol system will be best understood with reference to theaccompanying drawings, in which the apr paratus is illustrated in itsinoperative condition. Assuming that the ,car isat the iirst rloor,selected plugs are iirst inserted in the terminal f board illustrated inFigs. 4 and 10, If the plugs are inserted at 22, `23 and 42 to completea lcircuit indicated by the full lines, the car may` switch 62, up limit*switch Ll,relay coilUR, and',

up circuit relayy 66 to' line conductor B. Floor relay V12 upon closingmaintains a self-holding circuit through interlock 12-inwhich interlock.shuntsV the iioor selector switch 1U. Acircuit is established also fromline conductor A through interlock 12-in, contact member 12a of iloorrelay 12,l floor switch 64, `lifniitfswitch L2, Yrelay coil U51 andswitch 60 to conductor B. Sinnv ilarly, relay USz is energized throughswitches,

12b and 65. The operating coil ior'relay contact members 60 and 60 Aaredesignated bythe charn` acters d0` (see Fig. 5).

Referring to Figs. 2, Sand 10 and limit switches.` A circuit is Sestablished ythrough interlock BR-in for relay coil R' as Vindicated inFig. 3, Wherebyrelay R is Apicked rup and maintains a selholding circuitfor itself. This relayrinterrupts a circuit through the floor selectorswitches and therefore, when the elevator proceeds to the second. iloorVitis automatically stopped by means of the `floor stop switches, 64, 65and 62. These switches are `progressivelyopened to dropoutV relays USz,U81,

UR and floor-relayv 12.V Themfunction of the Q speed relaysUSi and USzwill be described later.

When the door is opened, relaycoilR is deenergizedland switch R againcloses permitting floor relay 14 to be energized when the doorV againcloses. n Y Y `second iloor is-v again closed, theY elevator carTherefore, whenthe door at the may in a similar manner proceed to thenext vstopping.pointyvhich in this case is the four h- --loor. yTheoperating circuit now extends from Y' v v it will be. noted that closureof relay UR, as above indicated, energizes theoperating Vcoils 2 and 4ofthe' direction switches 2 and 4, as well as the oper-Y ating coilsLBR'v and FR of the Ybrake and the afield relays BR and FR through theemergency conductor A through switches X, R, up-circuit relay 60, floorselector switch 2U, conductor 40, relay coil 14, hoor-stop-switch 66,hatch limit switch L1, relay URand switch 60 to conductor B. Relay 14 isself-holding through interlock 14-in and it also effects theenergization of relay coils US1 and U82 through its contact members 14aand 1417. The car in its upward motion passes the third floor withoutstopping, since conductor 30 is open-circuited fat the terminal'board. n

VThe car proceeds to the fourth oor, whereupon the correspondingfloor-stop switches 68, G'l'and 66, are `successively opened to drop outv.relays USz, USi, UR and 14, thus bringing the car to rest. When thefourth floor door is opened, relay coil R' is again'de-energized andkclosing the door. Thereupon, a circuit is established for the iirfthfloor relay coil 15 ,extending throughloor selector vswitch 4U,conductor ,50,7 relay coilv 15, limit lswitch L1 and relayV UR. Relay 15is likewise provided with a self-holding circuit through interlock 15-in andin turnit picks up relayUSi and `USz to accelerate the elevatortoward the fth floor. Y ,l As the car approaches the fifth floor, limitswitches La, L2 and L1 are operated progressively to slow down and stopthe car. The .opening of relay rUR brings. thecar to rest. Y

VIn the foregoing description .of operation, I, have assumed thattheelevator in each case has stopped Vsubstantially level with the Hde,-siredV floor. If inV any case, the proper` level is not attained, itiscf course automatically ef iected in a familiar mannerv bymeans of thelevelling switches UL andDL lwhich are. conup and the down relays URandDR for controlling the operation of the direction switches, Thelevelling switches UL and DL are mounted on bell-crank levers, the otherends of which are 161 in the hatchvray, ior opening the switches. Thebell-crank levers are mountedto rotate about pivot points 103 and theswitches are normally, held in their closed position by the springsli.The magnet coilsUL Aand DL are connected iny series circuit relation-andwhen energized,` operate the bell-crank levers to open the switches andretract the cam rollers S102 to a posif tion where they will pass thehatchway cams 101 without 4being operated thereby, When the coils DL andUL are de-energized, upon Open-v; ing oi the car door at a givenlanding, the

nected inA circuits .respectively paralleling theA Aprovidedwith camrollers 102 for engaging cams: Y

springs 104 `tend to closethe switches should 'Havingmade clear theessential details of the automaticstarting andrstopping of theelevator.. I will now refer to automatic speedcontrol featuresthatarenot essentialfor slow-speed elev vators butbecome 'of importancein high-speed operation. lReferring*to-Figs. 2, `3 and. 9, the closureof relay UR initiates the elevator operaf4 -toniat-siowispeed. when:relay Usi closes, the actuating coilof relaylRiis fenerfgized to-cau'se Athe relay to-.connect the `fcoil @F1 of generator iield relayacross ithe 'x'riotor arma'ture. ArelayiGl, 'which iis 1 controlled in:accordance with the .counter 1E.M.`F. -of the motor, fcloses 'to shunta portion o'f the Eillustrated'generator iieid -resistor, therebyincreasing the lgenerator voltage andthe'dnotorspeed. When relay US:operates, -it le'rii-irg'izes irelay 2R, which inturn connects frelayAMF across the Amotor armature. This relay may be vv--adapted to r`closeat Na'ihigher voltage than relay lGF-vand, when `vclosed, f it-de-en'ergizes 'relay -F'Ri which disconnects the motor field windinglFi, to thereby further increase the motorspeed. Deceleration of themotor lispas Apreviously l'indicated, effected 'by the operation -of the'iie'ld relays in a reverse order.

With the terminal-'board arrangement illus'- trated in Figs. 4, l vand`11 lthe car, in Vits/downward movement, will stop at-ithe fourth,second and-rstoorslonly 'I'hecontrol'operations during fthedown movementcorrespond to 'those described for theupward travel with the exceptionthat the Apush-button station must be Ioperated for down vmotion tomaintain relay 61 closed,

and the 4floor selector switches 5D, 4D and 2D become effective. Thatis, selector switch D establishes a'circut to conductor 40 forcontroland DSz ling relay `14 and relays -DR, DS1 through thedown floorstop switches 71, `'l2 and '73. The car starts downward, upon theclosure ofthe fifth-floor door, the door switch completing a circuit forfloor relay :14 and relay DR, whichlcontrolbrake and field relays BR andFR and direction switches `1 and 3. downward and stops at the fourthfloor upon the opening of Pthe down oor-stop switches 71, 72 and '7-3.After starting from the fourth floor, thecar Willcontinue to the secondfloor Without stopping at the 4third Ifloor, since thefthird -floorcircuit is open at the terminal board. In like manner fthelcar `isstopped at the second yfloor. At Ethe ni-st iioor it isstopped by meansof the limit switches L5, k'L6 and L7 respectively,v in a similarmanner-to'that described -for the-upward travel.

"The schedule `of operation may be altered byy changing the'conn'ectionsatthe terminal `board as, lfor examplejwhen connected as per the dottedlines, the car when leaving'the rst iioor, willstop atjthethird andfifth floor going up and the third'and` -rst `oors coming down.Different stops'may be made comingdownfthan going up,suchasifollowingthe dotted line v'connections up for the first, thirdand'l'thiloors and coming down through 'the fuse of the solid lineconnections, stopping at the fourth, fsecond andffirst floors. g

My system lmay be further employed incon-y neotion with a 'push-button.control system, Vthe control circuits of which are indicated principallyin Figs.A 5 and 6, in conjunction with Figs. land 2. rl`he push-buttoncontrol systeinis` also illustrated vin Fig. '11 when considered inconjunction With Figs. 9 and 10. Itwill be observed thatjconductors i110to 125,` inclusive, )and conductor A, terminating at "thelowermostportion of Fig. `9, are continued-in Fig. -10 as conductors havingrespectively corresponding reference numerals. `Hence, the-applicationoffFigyll to Figs. 9 and 10 y consists in connecting -'conductors shown'in Fig. 11 to conductors having `corre- 1n-consideration ofV Fig. S131,iit y isl to l' be `understood The car startsV that the :terminal plughoard illustratedin Img. Y10 has substituted therefor the Eterrni'ndlplug board :illustrated vin Fig. 41l. `Reference Acharactersusedinterminating :parts yin Figs. 1 fto 'l fare usedto iter-minatacorresponding pats in lFigs. 19, l0 and 11 .with 1the exception that'the f additional reference connection U11, e132, U2, fet'c.,1have beenusedto indicate the pushbuttonsasso'ciated with tively. For thisoperation, switch X in llgS, remains open.v An'up and down push buttonswitchlllisprovidedfineach car. There Ais also required fanauxiliaryfloor relay for each 'loor. The system illustrated is arrangedyfor 'the 'operation oi ithree cars serving five floors.

Theauxiliary relaysV are indicated in the tollowing imanner: 21'RD isrthe auxiliary down relay foriio'or 2, car l. l22RD 'is the auxiliarydown :relay `for oor 2, car 2. 'Similarly 21RU is theauxiliary up relayfior floor 2, car -l; 22RU is theauxiliaryup relay for iloor 2, car V2,Pand the other Vrelays vare correspondingly designated. These rrelays:are Vprovided withA normallyv closed contact members in the floorselectorcircuits (see Figs. Bland 11) andare also provided withself-holding interlocks. In thefcarisprovideda stop and start button,such-as 82, 83 Vorli'fifor each lintermediate iioor connected betweenconduotorA and the floor selector contactfmembers 1U, 2U, 2D, etc. Anauxiliary set'of door switches is' connected inthe hall :push-'buttoncircuits. Fig. 7 `illustrates a suitab1e door Yswitch "72, two

of .which are required for each floof, one Jior eachdirection Vofoperation;r The coils of these door switches are'energized by means .ofthe Vup and down push-buttonsvl located ineach car. When -any coil Aisenergized, the switch vroller is moved down to engaging `position withthe corresponding door. When the door is opened the switch contactmembers are broken by the lifting of contact kbar -72 by the roller'72". This arrangement is :such that the stopping 'of cars movingdownward, does not interfere with v a call .toup-going cars.

f -Assuminga car at the 'rst iioor with selector switch' 1U closed,(Fig. 6) upon the closure of the ldoor a circuit is established throughswitch 1U to conductor 20, floor relaycoil 12, (Fig. 3) and iioorstopcontact members 62,64 and rto energize relays UR, US1 and USzasfor`the previously described operation. The car will start upward andcontinue to the top iioor, since-convtactmemberR is provided with ashunt circuit closed'by contactmembers VBR--fin (see "-Fig. 6) unlessthe-car operator pushes vastop-button to open its normally closedcontact vmembers' or unless there is a `call by-a waiting passengeroperating one ofthe hall-buttons. If the car operator 'pushes thethird-floor stop button 183, affcircuit to conductor v'40 is interrupted:and the In order to again proceedit is necessarylto move vthe-operatedstop-button Ito `again close its 'contact members, yafter which'the.-floor-selectorswitches?automaticallyIcontinue` the move-v y, terminedschedules.l

lup by-pass button 86 incar 'by those familiar with the art.

relays AIRU, 42RU and 43RU are immediately energized and held in throughtheir holding interlocks. The operationr of these relays effects theopening o1r conductor 50, as illustrated vin Fig. 6, and this'corresponds to an operation of the stop` button, since these' switchesare in `series. relation. Therefore, car No. 1, when reaching the fourthfloor will stop. Onffeachcar is provided a pair of by-pass buttons, 86and 87 one ion upand one for down, so that should the operator actuatethe No. l, the car will not stop' at the fourth floor butthe nextsucceeding car No. 2 or car No. 3 as the case may be, will stop at thatfloor. yWhen any vcar stops at the rfloonthe opening of the doorinterrupts the holding circuits of `the auxiliary iloor relays such as41H17, `fiZRU and 43RU, and thereby restores the circuits ofall thecars. In other words, the first car to stop automatically cancels.`thecall tothe remaining cars.V The opening of the door does not,xhowever, cancel '-25'V matic levelling feature vpreviously alluded tomay be incorporated in this system, as illustrated, since the levellingsystem isV independent of the regular operating means, when the car iswithin thestopping zone androperating at low speed; Theiirstembodirnentof my system; as described, may be advantageously employed in connectionwith a plurality of elevators under conditions where it is desirable tomaintain prede- The maintenance ofr deflnite schedulesl is wellunderstood and appreciated The further adaptation oifmyA system for au-ftomatic push-button-'control is Vparticularly desirable for high-speedservice, wherein an operatoris preferably maintainsdv in each Ycar sothat in order to maintain a proper schedule or permit a full car tocontinue uninterrupted, the sysand stops at the mostremote point.,Furthermore, in accordance with my system, the stopping of the car does`not cancel the calls pre,- viously set up'for other Vfloors.

Variousmodiiications may] be made by'those skilled in the artwithoutdeparting from the spirit and scope of myinvention,` which has been'vdescribed in preferred formfand illustrated, diagr'ammaticallyy in amanner that is easilyunderstood. I-.desira thereforartobe limited Aonlyin L accordance with the appendedV claims.

r I' claim as my irn/ention:v f

1.; In an elevator system,.the combination with a car andcontrollingmeans therefor, of aplurality of floor-.relaysior dispatching theY carto all iioors,I switches 4actuated by the `car for controlling saidrelays'and a plurality of man-` ually operable, switchesffo'r excludingcertain 2. In an elevator system, the combination with a car and'controlling means therefor, a plurality of 'floor-relays fordispatchingV the car lto all doors, a pluralityl of' manually operableswitches for excluding, certain floors, and additional means foreffecting and maintaining a? predetermined car-levelV at each floor. Y

3. In an elevator system, the combination with a car and controllingmeansl therefor, of a plurality of floor-'relays for dispatching the carto all floors, switches actuated by the car forcontrolling .saidrelays., a plurality` of manually operable vswitchesy for excludingAcertain iloors, and additional means foreiecting and maintaining apredetermined car-level at each floor. 4. In an elevator system,` thecombination with a plurality of cars, of means for initiating the fmeans for cancelling any call and transferring" said call to other cars,and meanscomprising a pairof electro-responsive door switches at eachfloor for preventing interference between up and down calls.

A5. In,V an elevator-control system, a car con-k troller vcomprising amain control lever, con-- tacts for up `motion and contacts forY downmotion, a motor and drive gear for the actuation of said elevator,cooperating control means including contactors connectedbetween saidcarv controller and said motor for the control thereof, and Van auxiliarycontrolmeans incorporated in said controller for the independentactuation of said .control means for stopping and starting the carduring the travel in a given direction while said main control leveroccupies an operating position. 6. In an elevator-control device, a.controller having contact members i'orthenormal control thereofincluding selection between vupward and downward directions,andauxiliary contact `members for the actuation of auxiliary controlVdevices to stop and start-said elevator without moving vthe controllerfrom operative position.

7. In an elevator-control device, a controller element'comprising main'control members for determining the direction of travel, and auxiliarycontrol memberseifective to stopnandstart `in a given directiononly-without movementof the main controll element from its operativeposition; and means for rendering; saidauxiliary members effective kwithrespectgto a `floor-levell 8. An elevatorinstallation comprising amotor, a'control circuit therefor-including a starting switch,y and anormally closed automatically operable 'stoppingA switch forl openingthe circuit through the motor at a predetermined point in itsoperation,a by-pass around'said stopping switch,`;a magneticcoil common tothe maincontrolcircuit and the circuit throughfsaid bypass, a switch in saidby-pass which is normally closed so that the stopping switch isineffective to stop the motor, and amagnetunder manualv control to. openthe. Vby-passV switch to render said stopping' switch effective.`

9. Anelevator installation comprising a motor, a control rcircuittherefor including a starting switch. and a normally closedautomatically operable stopping switch for opening the circuit throughthe motorV at a preselected point in its Yoperationa by-pass around saidstoppingr switch, a switchin said'by-pass, a magnetic coil forcontrolling lthe -by-pass switch which is'held open when said coil isenergized,

thereby renderingV said automatically operable l stopping switcheffective tosto'p themotor after the switch in theV by-pass has beenopened, and

manually controlled meansjfor interruptingithe circuit through saidcoil, thereby permitting the by-pass switch to close and rendering thestopping switch ineffective.

10. In an elevator controller a master control lever, and cooperatingcontacts for operating the car, an auxiliary switch, and auxiliarycontacts for the actuation of auxiliary motorcontrol circuits while ythecontrol lever occupies an operating position.

1l. In an elevator controller, a master control lever and an auxiliarycontrol push-button including auxiliary contacts for the actuation ofauxiliary control circuits, and means comprising circuits and contactorsfor slowing down and stopping said elevator car upon the actuation ofsaid push-button when said control lever is in operating position andfor resuming travel in the same direction upon the release of saidpush-button.

12. In an elevator installation comprising anv electric motor,electromagnetic means, for controllingthe current to the motor, astarting switch for energizing said means, means for maintaining currentthrough said means after the starting'switch has been operated, anautomatically operated floor switch for interrupting thevcurrent throughsaid means at each floor, a by-pass for a oor switch, a normally closedswitch in the by-pass, and manually controlled means for opening saidby-pass switch.

13. In an elevator installation comprising an electric motor,electromagnetic means for controlling the current to the motor, astarting switch for energizing said means, means for maintaining currentthrough said means after the starting switch has been operated, anautomatically operated floor switch for interrupting the current fromsaid means at each floor, a by-pass for a oor switch, a normally closedswitch in the by-pass, electromagnetic means for opening the by-passswitch, and

Vmanually controlled means forl energizing the last said electromagneticmeans.

14. In an elevator-control system, an elevator, motive means for saidelevator, a control device on said elevator actuable from a normal to asingle-circuit-closing position, starting-control means for saidmotivemeans operably responsive to an actuation of said control device,speedcontrol means for said motive means controlled vby said controldevice, and means for delaying the operation of said speed-controlmeans, whereby said speed-control means is responsive only to asustained actuation of said control device.

15. In an elevator-control system, an elevator motor having a separatelyexcited iield winding, a generator having a separately excited fieldwinding for supply power to said motor, means for starting andaccelerating said motor to a predetermined high speed including meansforv increasing the excitation of the generator ield winding in stepsand for decreasing the excitation of said motor field winding, andspeedresponsive means for rendering the decreasing of the motor fieldexcitation and the highest of the steps of generator excitationineffective while the speed of said motor is below a predeterminedintermediate value. y

16. In an elevator control system, an elevator motor, a generator havinga field winding for supplying power to said motor, means foraccelerating said motor through a predetermined speed range includingmeans for increasing the excitation of the generator eld winding in aplurality of steps and speed-responsive means for rendering the highestof the steps of generator excitation ineffective until the motor attainsa predetermined speed intermediate the limits of said range.

EDGAR M. BOUTON.

